When a user enjoys a certain service, identification (authentication) is performed to identify whether the user is a valid user qualified to enjoy the service, and key sharing is performed for cryptographic communication. One type of cryptographic algorithm is used in cryptographic communication, and authentication and key sharing cannot be performed between devices implementing different algorithms.
Further, there is a reference describing a communication system wherein a plurality of protocols for cryptographic technology application can be employed (JP10-304333).
Additionally, there are references describing technologies utilizing a plurality of algorithms (JP2000-151578, JP5-227152).
As stated above, conventionally, one kind of cryptographic algorithm has been used in cryptographic communication, therefore, when the algorithm is found to be vulnerable or is broken, or when security (safety) with data encryption cannot be held due to leakage of keys or the like, a securer algorithm etc. is to be implemented. In such a case, it may happen that different algorithms are implemented by devices, and there has been a problem in that authentication and key sharing cannot be performed between such devices implementing different algorithms, as referred to above. Also, since different cryptographic algorithms are provided by each manufacturer or the like for a market etc., there has been a problem in that authentication and key sharing cannot be performed between devices implementing such different algorithms.
Moreover, there has been a problem in that when the security (safety) is not being maintained any more, a securer algorithm is to be implemented as mentioned above, which may result in a case where the existent systems and devices become unusable by implementing a new algorithm etc.
Additionally, there has been a problem in that even if a more sophisticated algorithm is to be devised in the future, the algorithm cannot be applied to the device which has been used.
It is an object of the present invention to resolve problems such as impossibility to perform the authentication due to difference of installed algorithms.
It is another object of the present invention to allow a system and a device to remain operable even when an algorithm has been made unusable due to breaking of the algorithm or the like.
Further, it is another object of the present invention to reduce the risk of decrease in security due to breaking of the algorithm or the like, by allowing a system and a device to remain workable.
Additionally, it is another object of the present invention to reduce the chances of invalid decryption being performed by eavesdropping etc., and to improve the security.